This invention relates to a process for purifying a hydrogen peroxide aqueous solution, which comprises bringing "a hydrogen peroxide aqueous solution containing a large amount of phosphoric acid, etc." obtained by extracting with water a reaction mixture prepared by a method of forming hydrogen peroxide by an oxidation-reduction process of anthraquinones (the so-called anthraquinone process) into contact with specific active alumina particles at a relatively low temperature for a specific time, and can remove a phosphoric acid component from the above hydrogen peroxide aqueous solution with a high rate substantially without causing decomposition of hydrogen peroxide.
As a method for preparing a hydrogen peroxide aqueous solution, there has been generally employed a method in which a hydrogen peroxide aqueous solution is obtained by extracting with water a reaction mixture prepared by a method of forming hydrogen peroxide by an oxidation-reduction process of anthraquinones (the so-called anthraquinone process). In the above preparation method, phosphoric acids have been frequently added for various purposes.
In the prior art, as a method for removing an acid component such as a phosphoric acid component, sulfuric acid and acetic acid in a hydrogen peroxide aqueous solution, there has been known, for example, an ion exchange resin method in which an acid component is adsorbed and removed by using an ion exchange resin such as Amberlite (produced by Organo K. K.), etc. as disclosed in Japanese Patent Publication No. 3002/1964. In this method, although an acid component such as phosphoric acid can be removed, there involves a problem that ion exchange resin particles themselves are decomposed by hydrogen peroxide, and become unusable after several times of regeneration, so that the method was not practical.
As a method for removing a phosphoric acid ion component in a hydrogen peroxide aqueous solution, there has been disclosed in U.S. Pat. No. 3,664,812, a precipitation method in which phosphoric acid ions in the above hydrogen peroxide aqueous solution are reacted with an alkali earth metal compound such as a calcium compound, a barium compound, a magnesium compound, etc. under basic condition (pH 7 to 8.5) to form precipitates of calcium phosphate, etc., and the precipitates are removed by filtration. However, in the above precipitation method, since a reaction mixture becomes basic, there is a problem that hydrogen peroxide is extremely easily decomposed.
In Japanese Patent Publication No. 41158/1973, there has been disclosed an adsorption method in which a hydrogen peroxide aqueous solution substantially containing no phosphoric acid is purified by bringing the solution into contact with active alumina at about room temperature for a short time of 1 to 5 minutes so as to remove minute amounts of metal or organic impurities by adsorption, for the purpose of stabilizing a hydrogen peroxide aqueous solution by removing the above minute amounts of impurities in the hydrogen peroxide aqueous solution.
However, the above adsorption method using active alumina does not have any specific disclosure about a hydrogen peroxide aqueous solution containing an excessive amount of a phosphoric acid component (PO.sub.4). Thus, it has not been known at all whether a phosphoric acid component can be removed with a high removal rate or not when using the above hydrogen peroxide aqueous solution containing an excessive amount of a phosphoric acid component which remains after used for various purposes. Further, the above method involves problems that considerable loss of active alumina is caused when the above active alumina used for adsorption of a phosphoric acid component and thus being in a saturated state is regenerated by removing a phosphoric acid component with an inorganic base aqueous solution, or when regenerated active alumina is reused for removing a phosphoric acid component in a hydrogen peroxide aqueous solution, hydrogen peroxide is decomposed and a hydrogen peroxide aqueous solution which is a final product is contaminated with considerable amounts of components which corrode storage containers made of alumina, whereby quality of a hydrogen peroxide aqueous solution is worsened.